Five or six years ago I spoke with Dwight Stevenson (perhaps it's "Stephenson") at Neumann USA about ordering replacement capsules for the KM 86, and he told me that the requirement for pair matching causes an extra surcharge (10 to 15%) to be added to the normal price for a pair of KK 84 capsules. He also told me that regular KK 84 capsules (with full-length pins) were available selected for pair matching at a similar surcharge. And as people who've seen the YouTube video about manufacturing the U 87 will have noticed, the halves of the capsules are selected and matched for exactly the same reason. The USM 69 stereo microphone similarly uses a selected, matched pair of K 67 capsules, which incurs a similar surcharge over the cost of "any two" K 67s if the capsules need replacement.
No manufacturer of condenser microphones has yet been able to manufacture capsules so consistently that they don't require selection and matching for critical applications. To claim otherwise is somewhere between "believing your own marketing" and dishonesty. It's only a question of the application and what the selection criteria are.
If a given type of microphone synthesizes its figure-8 pattern from two cardioids, and if that pattern is to be truly symmetrical, then either the two cardioid capsules must have essentially identical sensitivity at all frequencies that you care about, or else you'd have to build some kind of trimming circuit into the microphone. There ain't no other way.
--best regards